1. Field of the Invention
This invention relates to a rubber laminate having improved barrier properties to fluorocarbon and other gases and improved flexibility, and more particularly, to a gas barrier rubber laminate suitable for forming rubber hoses and air springs for use in air conditioners using fluorocarbon gas refrigerant.
2. Prior Art
Rubber hoses are widely used in automobile fuel systems, torque converters, power steering systems, air conditioners, refrigerators, and propane gas supplies as well as ordinary household uses. The rubber hoses are intended to pass a variety of media such as water, oil, organic solvents and gases and in all cases, required to be fully resistant to the media. Especially high pressure hoses for use as refrigerant tubes in building and automotive air conditioners are desired to exhibit improved impermeability to fluorocarbon and other refrigerant gases while remaining fully flexible.
However, the gas filled in the refrigerant tubes gradually penetrates and escapes through the wall of the rubber hose. It was thus necessary in the case of automotive air conditioners, for example, to re-charge the system with refrigerant every 4 or 5 years.
To improve the gas impermeability of rubber hoses, there were proposed a number of methods including (1) to increase the amount and wall thickness of rubber used, (2) to coat the rubber hose inner surface with nylon film (see Japanese Patent Application Kokai (JP-A) 123661/1984 and 113885/1985), and (3) to cover a nylon inner tube with rubber to form a hose (see JP-A 113882/1985). Beside from the rubber hoses, it is known that plastic films are improved in gas impermeability by (4) using a coating of organosilane as a gas barrier film (JP-A 112635/1987 and 286331/1990). However, method (1) has the problem that increased gage leads to an increase of product weight, an increased cost and a loss of flexibility. Impermeability to gases is improved to a limited extent. Methods (2) and (3) are insufficient in gas impermeability. Especially method (2) is difficult to continuously manufacture rubber hoses and a conventional combination of rubber with nylon or the like cannot fully satisfy the properties required for rubber hoses such as refrigerant tubes. Method (4) has the difficulty in using an organosilane coating as a gas barrier film in applications where significant deformation occurs.